The disclosure of Japanese Patent Application No. 11-288745 filed on Oct. 8th, 1999 is herein incorporated by reference.
The present invention relates to a substrate dropping prevention mechanism provided in a substrate inspection device used in inspection of the underside of semiconductor wafers etc., and to the substrate inspection device.
Conventionally, a wafer inspection device for carrying out macro observation has been used in observation of the upper and lower surfaces of a semiconductor wafer etc. With this type of inspection device, the underside of a wafer is held by vacuum suction, and the underside is turned upward to facilitate observation and inspection. For this reason, with this inspection device, as shown in FIG. 7, a plurality of vacuum suction pads 2 are provided on an arm 1, and the wafer W is sucked up or set down under solenoid valve control (not shown).
A pivot section 3 is provided at one end of the arm 1, and as shown in FIG. 7 and FIG. 8, a shaft 4 is fixed in a horizontal state to both sides of the pivot section 3. The both ends of the shaft 4 pass through support members 5, 6 of the substrate inspection device so that the arm 1 is capable of rotating around the shaft 4. As shown in FIG. 7, FIG. 8, FIG. 9A and FIG. 9B, a pulley 7 is fixed to an end of the shaft 4. A pulley 9 is also fixed to the axis of rotation 10a of a motor 10 fixed to a base plate 11. A belt 8 is wound around the pulley 7 and the pulley 9. If the motor 10 rotates the pulley 9, the arm 1 is swung and is stopped at any desired angle, as shown in FIG. 9B, then the underside of the wafer W can be inspected. This type of inspection device is generally used in combination with a conveying device.
However, with the inspection device of the related art, there are the following problems. When the wafer is tilted, that is, during the operation of moving from the horizontal state to the inspection angle, during inspection at the inspection angle, or during an operation of moving from the inspection angle to the horizontal state, if the vacuum suction is defective, the wafer will fall off and is likely to be damaged. Here, defective vacuum suction is caused by, for example, the vacuum being cut off, or malfunctioning etc.
An object of the present invention is to provide a substrate dropping prevention mechanism so that a substrate does not fall off even if vacuum suction becomes defective, and a substrate inspection device provided with the substrate dropping prevention mechanism.
The present invention is applied to a substrate dropping prevention mechanism fitted to a substrate holding device provided with a holding section for holding a substrate by sucking a first surface, and a tilt mechanism for tilting the holding section.
The object described above is achieved by providing a dropping prevention member moving between a support posture for supporting a substrate that has come away from a support section, and a retracted posture that is different from the support posture, and a movement mechanism for setting the dropping prevention member to the retracted posture when the substrate is substantially horizontal with a first surface facing downwards and a second surface facing upwards, and setting the dropping prevention member to the support posture when the substrate is tilted over a specific angle with respect to the horizontal by the tilting mechanism.
The dropping prevention member has a first dropping prevention surface, confronting a peripheral surface of the substrate, and a second dropping prevention surface, confronting the second surface of the substrate, and the first and second dropping prevention surfaces are preferably formed so as to respectively confront the peripheral surface and second surface of the substrate when the dropping prevention member is moved to the support posture. The second dropping prevention surface preferably confronts the second surface of the substrate with a specified gap between them.
A moving mechanism can cause movement of the dropping prevention member between the retracted posture and the support posture by interlocking with a operation of the holding section using the tilt mechanism. In this case, the dropping prevention member is constantly urged to the support posture side under spring force, and can be provided with a linkage member for moving the dropping prevention member to the retracted posture against the biasing force of the spring when the holding section is rotated to the horizontal state. Also, when the holding section in the tilted state is moved to the horizontal state, the linkage member moves the dropping prevention member to the retracted posture opposing the spring force, while when the holding section in the horizontal state is moved to the tilted state, the dropping prevention member is moved to the support posture by the spring force.
The dropping prevention member is preferably formed from a plurality of dropping prevention parts provided at specified intervals on the holding section. The plurality of dropping prevention parts are arranged and postured so that conveyance of the substrate to the holding section is not prevented when moved to the retracted posture.
More specifically, in the case where the substrate is a wafer, the holding section is formed from a flat bracelet shaped plate that is partially cut away, and fits the outer shape of the wafer, suction sections are arranged at predefined intervals on one surface of the bracelet shaped flat plate, and the dropping prevention parts are arranged at predetermined intervals on the bracelet shaped flat plate so as to prevent the substrate dropping off from the one surface of the bracelet shaped flat plate.
A substrate inspection device for carrying out visual inspection of upper and lower surfaces of a substrate according to the present invention achieves the above object by providing a holding section for holding a substrate by suction using a suction section, a tilting mechanism for tilting the holding section so as to move the substrate between a horizontal state and a tilted state, and a substrate holding device having the substrate dropping prevention mechanism as described above.